Method and apparatus for shaping edges

ABSTRACT

Method and apparatus for shaping the edge ( 103 ) of a rigid, brittle materials such as ceramic plates and rigid composite plates utilizing a resin-bonded abrasive wheel.

FIELD OF THE INVENTION

[0001] The present invention relates to a method and an apparatus for shaping the edges of rigid, materials such as ceramic plates and rigid composite plates.

BACKGROUND OF THE INVENTION

[0002] Numerous glass plate components and rigid print-circuit boards are used for display windows or LCD panels, respectively, in precision devices such as portable phones, pagers, and hand-held computers. These glass plate components and printed circuit boards are disposed in a complex manner in a narrow space together with other precision components. Further, an LCD panel or the like is typically coupled with a glass faceplate and a flexible printed circuit board.

[0003] Typically, numerous cracks and/or defects (sometimes referred to as “fine splitting” are present in the cut surface of rigid, brittle materials such as ceramic plates, rigid composite plates (including rigid printed circuit boards) immediately after cutting. Numerous pits having a size of typically 1 to 50 micrometers are also typically present on the cut surface of rigid, brittle materials such as ceramic plates and rigid composite plates. In addition, the edge corners of the cut rigid, brittle materials such as glass plates are usually sharp. If such cut glass plates are used, for example, in the construction of precision devices, they may damage other device components. For example, the sharp edge corners of the cut glass plate may damage (e.g., cut into) flexible printed-circuit boards or other precision components. Cut surfaces of the glass plate may also cut the guide roll or carrier used to facilitate the assembly of the precision devices.

[0004] Further, glass fragments on the cut surfaces and/or the fine splitting, cracks, etc. present of the cut surface can lead to glass fragments separating from the glass plate into the assembly equipment and/or precision devices.

[0005] In addition, if cracks are present on the cut surface of rigid, brittle materials such as ceramic plates and rigid composite plates, the strength of the material decreases significantly. Therefore, the edge of component made of rigid, brittle materials such as ceramic plates and rigid composite plates are preferably finished so that they do not have corners, pits, or cracks.

[0006] Conventional techniques for removing the corners, pits, and cracks from the edge of rigid, brittle materials such as ceramic plates and rigid composite plates include abrading and of the edge of the material using a metal-bonded diamond wheel. The metal-bonded diamond wheel is an abrasive wheel in which abrasive diamond particles are bonded together with a metal binder. Since rigid, brittle materials such as ceramic plates and rigid composite plates are brittle, the cutting mode of the conventional techniques, which utilize rigid, non-elastic materials such as diamond wheels, is typically a “tear-type” or a “crack-type”. These cutting modes generally lead to the formation of numerous cracks and pits on the abraded surface, making it impossible to effectively remove the pits from the edge of the material. Moreover, in the case of relatively thin rigid, brittle plate (e.g., a glass plate) having thickness of typically less than 5 mm (for example, less than 1.4 mm for a glass plate), the formation of the cracks can lead to catastrophic cracking in the rigid, brittle plate (i.e., the plate breaks or shatters).

[0007] More recently, resin-bonded, diamond wheels have been used, for example, in place of metal-bonded diamond wheels, to shape the edge of glass plates (see, e.g., U.S. Pat. Nos. 5,975,992 (Raeder et al.) and 5,816,897 (Raeder et al.)). Advantages of resin-bonded, diamond wheels include increased wheel flexibility and elasticity.

[0008] The amount of abrading that occurs with conventional chamfering processes that utilize metal-bonded or resin, diamond wheels, can be controlled by adjusting the position of the metal-bonded, diamond wheel relative to the surface of material to be abraded. Further with regard to the conventional chamfering process, the amount abraded is determined by the position of the diamond wheel relative to the material to be abraded. This process requires frequent and precise adjustment of the relative positions of the diamond wheel surface and the surface of the material to be abraded. Such frequent adjustments become cumbersome. The position adjustments are typically facilitated using computer control (sometimes called, NC (numerical control) machining system) (see, e.g., Japanese Patent Laid-Open Publication No. 11-221763, published Aug. 17, 1999). The input of position data typically requires a relatively long period of time (e.g., 60 to 120 minutes).

SUMMARY OF THE INVENTION

[0009] The present invention relates to a method and an apparatus for shaping an edge (i.e., providing a surface of edge being free of pits) of a rigid, brittle material such as ceramic (i.e., glass, crystalline ceramic, and combinations thereof plates and rigid composite plates (including rigid printed circuit boards).

[0010] In one aspect, the present invention provides a method for shaping an edge of a material such as ceramic plates and rigid composite plates (including rigid printed circuit boards), the method comprising; abrading an edge of a material such as ceramic plates and rigid composite plates (including rigid printed circuit boards) in a predetermined abrasion amount, using a resin-bonded abrasive wheel under a load, and in contact with, the edge being abrading, wherein the abrasion amount is determined by controlling the load for pressing the material being abraded with the resin-bonded abrasive wheel. Preferably, the method according to the present invention is conducted such that the edge of the resulting abraded material is free of corners, pits, and cracks.

[0011] In some embodiments, the wheel has a width surface contacting the edge of the material being abraded, and during the abrading, at least one of (i) the width surface traverses along the edge of the material being abraded or (ii) the edge of the material being abraded traverses along said width surface.

[0012] In another aspect, the present invention provides an apparatus for abrading an edge of a rigid, brittle materials such as ceramic plates and rigid composite plates in a predetermined abrasion amount using a resin-bonded abrasive wheel under a load and in contact with the edge being abraded, the apparatus comprising a resin-bonded abrasive wheel, a mechanism for rotating the abrasive wheel, and a system for contacting and controlling, during the abrading, the load of the abrasive wheel on the material being abraded.

[0013] One embodiment of an apparatus according to the present invention is shown in FIG. 2. Apparatus according to the present invention 200 comprises abrasive wheel 201, driving shaft 202, motor 203, and pressure cylinder 204. Apparatus 200 and material to be abraded (e.g., glass plate 206 are arranged so that they can movable independently with respect to each other. Material to be abraded 206 may, for example, move in parallel to driving shaft 202 (the direction indicated by arrow) of the device during abrading).

[0014] Advantages of the present invention include being able to provide materials such as ceramic plates and rigid composite plates free of comers, pits, and cracks in a relative short period of time, as compared, for example, to conventional techniques.

BRIEF DESCRIPTION OF THE DRAWING

[0015]FIG. 1 is a perspective view illustrating the edge of a material to be abraded by the method according to the present invention.

[0016]FIGS. 2 A, B, and C are a front, side, and plane view, respectively, of an apparatus according to the method of the present invention for abrading the edge of a material to be abraded (e.g., a glass plate.

[0017]FIG. 3 is a photograph at 100× of the edge surface of a glass plate shaped according to the method of the present invention.

[0018]FIG. 4 is a photograph at 100× of the edge surface of a glass plate shaped by a conventional method.

DETAILED DESCRIPTION

[0019] The present invention may be suitable for shaping the edge of a variety of rigid, brittle materials such as ceramic plates and rigid composite plates. Examples of such glass plates include those used for precision device (e.g., portable phone or pager) display windows, LCD panels, or face plate. The thickness of the glass plate for such devices is typically from 0.2 to 1.4 mm, more typically for example, about 0.3 to 0.7 mm, or even about 0.3 to 0.5 mm. Rigid composite plates include those comprised of binder material such as polymer reinforced with fillers such as ceramic particles and fibers. Rigid composite plates include the substrate for rigid printed boards. Rigid printed circuit boards may have a mono-layered, or multi-layered, circuits (e.g., copper circuits). The rigid print-circuit board typically has a thickness of about 0.5 to 5 mm, more typically about 1 to 3 mm.

[0020] Resin-bonded abrasive wheels utilized in the present invention are abrasive wheels in which abrasive grains are fixed with a resin binder. Resin-bonded abrasive wheels typically exhibit flexibility and elasticity characteristics such that than can substantially elastically conform to the shape of the surface being abraded. Further, the cut mode is for abrading brittle glass plates according to the method and device of the present invention is typically a “shear-type”. Although not wanting to be bound by theory, it is believed that the lack of cracking, pitting, etc. in the glass plate surfaces abraded according to the method and device of the present invention is facilitated by a “shear-type” cutting mode. Further embodiments of the present invention are even suitable for relatively thin glass plates (e.g., less then 1.5 mm thick). Generally, the abraded surface formed by the cut mode of shear-type is referred to as “shear plane”. The shear plane is a smooth cut surface (mirror surface), and looks glossy.

[0021] Suitable resin-bonded abrasive wheels preferably have an elastic modulus in the range from 50 to 10,000 kg/cm², more preferably, in the range from 500 to 7,000 kg/cm². Although resin-bonded abrasive wheels having an elastic modulus less than 50 kg/cm² may also be useful, such wheels tend to wear out quickly. Further, use of resin-bonded wheels with an elastic modulus above about 10,000 kg/cm² tend to lead to the formulation of cracks or pits on the newly formed surfaces.

[0022] In another aspect, the resin-bonded abrasive wheel preferably has a Shore D hardness in the range from 10 to 95, more preferably, in the range from 40 to 80. If the Shore D hardness is below about 10, the abrasive wheel tends to wear out quickly. If the Shore D hardness is above about 95, there is a tendency for cracks or pits to be present on the newly formed surfaces.

[0023] The density of the resin-bonded abrasive wheel is preferably in the range from about 0.4 to 2.5 g/cm³. If the density is below about 0.4 g/cm³, the abrasive wheel tends to wear out quickly. For densities above about 2.5 g/cm³, there is a tendency for cracks or pits to be present on newly formed surfaces.

[0024] Examples of abrasive grains present in the resin-bonded abrasive wheels include conventional abrasive grains such as SiC, Al₂O₃, and CeO₂. Typically, the abrasive grains are screened and graded using the well known techniques and standards for JIS (Japanese Industrial Standard) grade (e.g., JIS (R6001, 1987 ver.) JIS 100 to JIS 10,000, preferably, in the range from JIS 220 to JIS 2,000, or the like). The abrasive grains generally have particle sizes (in conformity with JIS) in the range from about 1 to 125 micrometers preferably in the range from about 6 to 50 micrometers. It is also within the scope of the present invention to use abrasive grain graded to other industry recognized standards, such as ANSI (American National Standard Institute) and FEPA (Federation Europeane de Products Abrasifs).

[0025] The resin binder for the resin-bonded abrasive wheel is preferably polyurethane. A preferred polyurethane is a cross-linked polyurethane matrix such as disclosed in Japanese Patent Laid-Open Publication No. 294336/1990, published on Dec. 5, 1990, the disclosure of which is incorporated herein by reference. The cross-linked polyurethane preferably has a glass transition temperature greater than about 10° C., more preferably, in the range from greater than about 10° C. to 70° C.

[0026] Suitable resin-bonded abrasive wheel are commercially available, and/or can be made by techniques known in the art (see e.g., Japanese Patent Laid-Open Publication No. 294336/1990, published on Dec. 5, 1990, and U.S. Pat No. 4,933,373 (Moren), the disclosures of which are incorporated herein by reference.

[0027] An example of a commercially available resin-bonded abrasive wheel is that available under the trade name of “DLO WHEEL” from Sumitomo 3M Co., Ltd., Japan.

[0028] Abrasive wheels utilized in practicing the present invention typically have an outer diameter in the range from 50 to 500 mm, more typically, from 100 to 305 mm. The inner diameter of the wheels is typically in the range from 5 to 300 mm, more typically in the range from 10 to 127 mm. The width of the wheels is typically in the range from 10 to 500 mm, more typically in the range from 10 to 300 mm.

[0029]FIG. 1 is a perspective view showing the edge of a material (e.g., a glass plate) being abraded by a method according to the present invention. Material 101 is fixed such that the width of the edge to be abraded is parallel to with the axial direction of resin-bonded abrasive wheel 102. The outer peripheral surface of abrasive wheel 102 is under a load, and is in contact with, edge 103 for a predetermined period of time.

[0030] The load the abrasive wheel is under when in contact with the edge of the material being abraded is changed in accordance with the desired area and amount to be abraded. Since the resin-bonded abrasive wheel has flexibility and elasticity, the load for contacting the abrasive wheel with the surface to be abraded can be varied as desired over a range of loads. The load is correlated to the amount to be abraded per unit period of time. In other words, the amount to be abraded can be varied and controlled by adjusting the load. The amount to be abraded is also affected by, for example, by the abrading time and rotational speed of the abrasive wheel.

[0031] By contrast, a metal-bonded, diamond wheel, which is not flexible and elastic, does not allow for a range of loading, but rather is maintained at a substantially single, optimal value. Since the diamond wheel is rigid and non-elastic, if the load is even a little above the (substantially single) optimal value, the material (e.g., glass plate) being abraded typically breaks, Similarly, the load is even a little below the (substantially single) optimal value, there is no or insufficient abrading of the material. Hence, in conventional methods of shaping a material using a diamond wheel, the amount to be abraded cannot effectively be controlled by adjusting the load, but rather the amount being abraded is determined by the position of the wheel with respect to the surface being abraded.

[0032] Typically, the load for practicing the present invention is about 0.1 to 4 kg/50 mm (i.e., 0.1 to 4 kilograms based on a 50 mm wide wheel) (0.002 kg/mm to 0.08 kg/mm), preferably from 0.5 to 2 kg/50 mm (0.01 kg/mm to 0.04 kg/mm). The abrading time is typically 0.5 to 5 seconds, preferably from 1 to 3 seconds. The rotation peripheral speed of the abrasive wheel is typically about 100 to 2000 m/min. preferably from 200 to 1000 m/min. The contact angle, θ, of the abrasive wheel to the edge of the glass plate is typically from 0 to 60°, preferably from 30 to 60°.

[0033] The present invention can be further understood by FIGS. 2A-C. Device or apparatus 200 has resin-bonded abrasive wheel 201, driving shaft 202, motor 203, and pressure cylinder 204 placed on movable frame 205. Glass plate 206, which is to be abraded, is fixed to working table 207. Apparatus 200 and material to be abraded (e.g., glass plate) 206 are arranged so that they can movable independently with respect to each other. Material to be abraded 206 may, for example, move in parallel to driving shaft 202 (the direction indicated by arrow) of the device during abrading).

[0034] The load can be applied, for example, using a pneumatic pressure cylinder, and controlled, for example, using a system moderated by control system such as that available from Mechanotron Co., Ltd., USA under the trade designation “ACTIVE FORCE CONTROL SYSTEM”. The Mechanotron Co. device uses closed loop feedback to provide an adjustable constant force. It uses load cell or drive motor feedback to monitor force, and a microprocessor to continuously adjust the force to the desired setting. The device behaves similarly to passive devices, but is more effective at low forces, and exhibits faster response rates. It can be utilize linear or rotary bearings, with or without counterbalance weights. It can also be used for wrist mounted, or floor mounted devices. Further, the device can utilize any of a variety of actuators to control forces directly.

[0035] This invention is further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. Various modifications and alterations of the present invention will become apparent to those skilled in the art. All parts and percentages are by weight unless otherwise indicated.

EXAMPLES Example 1

[0036] A resin-bonded abrasive wheel (marketed under the trade designation “DLO WHEEL SERIES” by Sumitomo/3M Co., Ltd., Japan) was mounted on an abrasive apparatus as shown in FIG. 2. The elastic constant of the abrasive wheel was 1,000 kg/cm², and the density 1.5 g/cm³. The abrasive grains were JIS 600 graded SiC. The outer diameter of the wheel was 200 mm, the inner diameter 31.8 mm, and the width 50 mm. The glass plate (0.7 mm thick) was fixed to a working table. The edge of the edge of the glass plate was abraded under the following conditions. The rotational speed of the wheel was 1,500 rpm, the contact angle 45°, and the load 2 kg/50 mm. The abrading time was 2 seconds. Water was used as a lubricant.

[0037] The chamfer, C, of the abraded edge of the glass plate was 0.4 as measured according to Japanese Industrial Standard for Drawing). FIG. 3 is a photograph at 100× of the edge surface of the abraded glass plate. The black area in the lower half of FIG. 3 was the edge surface of the glass plate. The appearance of the abraded edge was smooth.

Comparative Example A

[0038] The edge of a glass plate having a thickness of 0.7 mm was abraded under the same abrasion condition as in the Example above, except the abrasive wheel was a resin-bonded abrasive wheel (marketed under the trade designation “DLO WHEEL SERIES” from Sumitomo/3M Co., Ltd.) having the following characteristics. The elastic constant of the wheel was 12,000 kg/cm², and the density was 2.5 g/cm³. The abrasive grains were JIS 600 graded SiC. The outer diameter of the wheel was 200 mm, the inner diameter 31.8 mm, and the width 50 mm. FIG. 4 is a photograph at 100× of the edge surface of the abraded glass plate. The black area in the lower half of FIG. 4 was the edge surface of the glass plate. There were pits such as conchoidal defects or pits present on the abraded surface of the glass plate edge.

Example 2

[0039] A type FR4 printed circuit board (i.e., a glass-epoxy resin printed circuit according to ASTM standard D1867-62T, the disclosure of which is incorporated herein by reference) having copper circuit layers on the both sides (1.6 mm thick) was fixed to a working table. The edge surface of the printed circuit board was entirely broken, and very rough (Ra=25.1; measured according JIS B0601, using a surface profile meter obtained under the trade designation “SEF30D” from Kosaka Laboratory Company, Japan). The edge of the print-circuit board was abraded with a resin-bonded abrasive wheel as described in Example 1 under the following conditions. The rotational speed of the wheel was 1,500 rpm, the contact angle 0 degree, and the load 2 kg/50 mm The abrading time was 4 seconds. Water was used as a lubricant.

[0040] After abrading, the edge surface of the printed circuit board was very smooth such that interface between the epoxy resin and glass fiber of the board had a very smooth surface roughness (Ra=3.9).

Comparative Example B

[0041] The edge of a printed circuit board (type FR4) was abraded as described in Example 2, except the abrasive wheel used was as described in Comparative Example 1 .

[0042] The edge surface of the printed circuit board after abrading was rough (Ra=13.2), and exhibited some glass fibers protruding from the epoxy resin matrix.

[0043] Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein. 

What is claimed is:
 1. A method for shaping an edge of a ceramic plate or a rigid composite plate comprising: abrading an edge of a ceramic plate or a rigid composite plate in a predetermined abrasion amount, using a resin-bonded abrasive wheel under a load and in contact with the edge being abrading, wherein the abrasion amount is determined by controlling the load for pressing the ceramic plate or the rigid composite plate with the resin-bonded abrasive wheel.
 2. The method according to claim 1, wherein the resin-bonded abrasive wheel has an elastic modulus in the range from 100 to 10,000 kg/cm².
 3. The method according to claim 1, wherein the resin-bonded abrasive wheel has a shore D hardness in the range from 10 to
 95. 4. The method according to claim 1, wherein the resin-bonded abrasive wheel has an elastic modulus in the range from 100 to 10,000 kg/cm², and a shore D hardness in the range from 10 to
 95. 5. The method according to claim 1, wherein the resin-bonded abrasive wheel has a density in the range from 0.4 to 2.5 g/Cm³.
 6. The method according to claim 1, wherein the resin-bonded abrasive wheel has an outer diameter in the range from 50 to 500 mm.
 7. The method according to claim 1, wherein the resin-bonded abrasive wheel has a width in the range from 10 to 500 mm.
 8. The method according to claim 1, wherein the load is in the range from 0.002 kg/mm to 0.08 kg/mm.
 9. The method according to claim 1, wherein the resin-bonded abrasive wheel has an elastic modulus in the range from 500 to 7,000 kg/cm², a density in the range from 0.4 to 2.5 g/cm³, a shore D hardness in the range from 40 to 80, an outer diameter in the range from 100 to 305 mm, and has a width in the range from 10 to 300 mm.
 10. The method according to claim 9, wherein the load is in the range from 0.01 kg/mm to 0.04 kg/mm.
 11. The method according to claim 9, wherein the glass plate etc. has a thickness in the range from 0.2 to 1.4 mm.
 12. The method according to claim 1, wherein the wheel has a width surface contacting the edge of the ceramic plate or the rigid composite plate being abraded, and wherein during said abrading, said width surface traverses along the edge of the ceramic plate or the rigid composite plate.
 13. The method according to claim 1, wherein the wheel has a width surface contacting the edge of the ceramic plate or the rigid composite plate being abraded, and wherein during said abrading, the edge of the ceramic plate or the rigid composite plate traverses along said width surface.
 14. The method according to claim 1, wherein the edge is an edge of a glass plate.
 15. An apparatus for abrading an edge of a ceramic plate or a rigid composite plate in a predetermined abrasion amount using a resin-bonded abrasive wheel under a load, and in contact with, the edge to be abraded, the apparatus comprising a resin-bonded abrasive wheel, a mechanism for rotating the abrasive wheel, and a system for contacting and controlling, during abrading, the load of the abrasive wheel on the ceramic plate or the rigid composite plate.
 16. The apparatus according to claim 15, wherein the resin-bonded abrasive wheel has an elastic modulus in the range from 50 to 10,000 kg/cm², a density in the range from 0.4 to 2.5 g/cm³, a shore D hardness in the range from 10 to 95, an outer diameter in the range from 50 to 500 mm, and has a width in the range from 10 to 500 mm.
 17. The apparatus according to claim 15, wherein the resin-bonded abrasive wheel has a density in the range from 0.4 to 2.5 g/cm³.
 18. The apparatus according to claim 15, wherein the resin-bonded abrasive wheel has an outer diameter in the range from 50 to 500 mm, and a width in the range from 10 to 500 mm.
 19. The apparatus according to claim 15, wherein the resin-bonded abrasive wheel has an elastic modulus in the range from 500 to 7,000 kg/cm², a density in the range from 0.4 to 2.5 g/cm³, a shore D hardness in the range from 40 to 80, an outer diameter in the range from 100 to 305 mm, and has a width in the range from 10 to 300 mm.
 20. The apparatus according to, claim 15 further comprising a mechanism for traversing a width surface contacting the edge of the ceramic plate or rigid composite plate during operation of the device along the edge of the ceramic plate or rigid composite plate.
 21. The apparatus according to claim 15 further comprising a mechanism for traversing the edge of the ceramic plate or rigid composite plate to be abraded during operation of the device along a width surface of the wheel contacting the edge of the ceramic plate or rigid composite plate. 